The computing power and functionality of mobile computing devices continues to increase rapidly. Various types of mobile computing devices are now commercially available which allow users to affordably and conveniently perform full-fledged computing and data communication activities while they are on the move. Today's mobile computing devices commonly integrate a wide variety of functionality including a plurality of different wireless data communication capabilities, a touch-sensitive display screen, one or more microphones, and one or more video cameras. Smartphones and tablet computers are two popular examples of such mobile computing devices. The number and types of mobile computing applications that are available to mobile computing device users are also continuing to increase rapidly, as is the number of people that regularly use a mobile computing device to perform their online computing and information management tasks. In fact, mobile computing devices have become a principle computing device for many people.
Authentication of the identity of a user of a mobile computing device is important to prevent an unauthorized person from masquerading as an authorized user. This type of identity theft can have devastating results such as loss of secure information, theft of products or services, and so on. Current authentication schemes for ensuring the authenticity of a user typically require a password from the user at the start of each session or after a period of inactivity. Some schemes wait a fixed amount of time before requiring re-authentication, which typically entails the user re-entering a password after this fixed amount of time elapses.